This invention relates to tufting machines and more particularly to tufting machine modular gauge parts having a construction which facilitates accurate and rapid location and positioning in the tufting machine and minimizes the tendency of a module to twist due to the forces applied during the tufting process.
In tufting machines a plurality of yarn carrying needles are mounted on needle bars extending transversely across the machine, the needle bars being reciprocated cyclically so that the needles penetrate and insert loops of yarn into a backing material fed through the machine. The loops formed are seized by either loopers or hooks mounted on a looper or hook bar depending upon whether it is desired to produce loop pile or cut pile in the material, and in the latter case loops seized by the hooks are cut by knives cooperating with the hooks. In the tufting art the gauge of a pile fabric is determined by the spacing between adjacent parts, i.e., the needles, loopers or hooks, and knives, of the tufting machine, such parts being known as gauge parts. The spacing between the needles, known as the pitch, is a measure of the gauge of the pile fabric produced. The needles and the loopers or hooks must be accurately positioned so that cooperation therebetween results in a loop being seized by the looper or hook. The term looper is used in the art in conjunction with uncut pile while the term hook is used in the art in conjunction with cut pile and those instances where both cut and uncut loops are formed. Thus, for convenience the term hook will be used hereinafter, it being understood to apply to hooks and loopers.
In fine gauge machines, i.e., those which produce fabric that have tufts which are closely spaced apart such as 0.1 inch or smaller, in order to increase the ease with which a faulty or damaged needle or hook can be replaced and to ensure that the requisite spacing is maintained either initially or during replacement of a damaged needle or hook, it has become common for small groups of needles or hooks to be mounted on a needle or hook module, such needle modules being illustrated, for example, in Parsons U.S. Pat. No. 4,138,956. A number of such modules may be removably mounted on the needle or hook bar in side-by-side disposition to form rows of needles or hooks on the needle or hook bar respectively. The removal and replacement of needle or hook modules necessitates that the new module or modules be positioned accurately on the respective needle or hook bar to ensure accurate cooperation with the corresponding gauge parts.
Conventionally a single central screw, as illustrated in the aforesaid Parsons patent, acts to secure such modules to the respective bar. Such a securing, however, renders it difficult to ensure accurate replacement of a damaged or worn module or modules and furthermore necessitates entire removal of the central screw from each module to be replaced. Additionally, the use of a central screw does not preclude a twisting about the screw when large forces are applied to the gauge parts and this can affect the accuracy of the cooperation between the needles and hooks. Another type of needle module in which a pair of spaced apart screws are received through bores in a flange beneath the needle bar and threadily received within the needle bar is disclosed in Czelusniak U.S. Pat. No. 4,574,716, but such an arrangement requires removal of both the screws in order to replace a single module and, additionally, since the screw holes may not be precisely drilled, location is not precise.